This invention relates to an automatic stop/start-up controlling device of an engine which is able to execute an idle stop.
Some vehicles are arranged with an automatic stop/start-up controlling device which is able to execute a so-called idle stop in order to reduce fuel consumption of an engine mounted thereon. The automatic stop/start-up controlling device of the engine controls to automatically stop the engine when a predetermined automatic stop condition is satisfied, for example when an accelerator pedal is not depressed, while the engine is driven. The automatic stop/start-up controlling device of the engine also controls to automatically start up the engine when a predetermined automatic start-up condition is satisfied, for example when a starting operation is executed, while the engine is automatically stopped.
Some vehicles are of a type commonly called a hybrid vehicle having an internal combustion engine and a motor-generator (described hereinafter as xe2x80x9cmotorxe2x80x9d) which is disposed between the engine and a clutch and is connected to an output shaft of the engine. The hybrid vehicles have improved startability of the engine by the motor regardless of having a series or parallel arrangement. In addition, some hybrid vehicles are arranged with an automatic stop/start-up controlling device which is able to execute the idle stop.
Such automatic stop/start-up controlling devices of the engine are disclosed in, for example, Japanese Patent Laid-Open No. 60-43145, Japanese Patent Laid-Open No. 60-43147, and Japanese Patent Laid-Open No. 11-257119. Such controlling device disclosed in Japanese Patent Laid-Open No. 60-43145 controls such that fuel is cut-off (a) when a throttle opening degree is less than a set value and a clutch is engaged, or (b) when the clutch is disengaged and the transmission is in neutral position, whereas the controlling device controls such that fuel is not cut-off (c) when a throttle opening degree is greater than a set value, or (d) when the clutch is disengaged and the transmission is in a position other than neutral. A controlling device disclosed in Japanese Patent Laid-Open No. 60-43147 controls such that fuel is cut-off (a) when a throttle opening degree is less than a set value and a clutch is engaged and a transmission is in the high-speed gear or in neutral, or (b) when a throttle opening degree is less than a set value and the clutch is engaged and the transmission is in a low-speed gear and engine speed is greater than a set value, whereas the controlling device controls such that fuel is not cut-off (c) when a throttle opening degree is greater than a set value, or (d) when the throttle opening degree is less than a set value and the clutch is disengaged, or (e) when the throttle opening degree is less than a set value and the clutch is engaged and the transmission is in low-speed gear and the engine speed is less than a set value. A controlling device disclosed in Japanese Patent Laid-Open No. 11-257119 controls to stop the engine of a hybrid vehicle when the clutch is disengaged and the gear position of the transmission is in a non-running position and the throttle opening degree is at substantially fully closed degree.
Since how long the engine is stopped is important in order to reduce the fuel consumption of the engine. For hybrid vehicles, conventional stop/start-up controlling devices of the engine control to stop the engine by fuel cut-off on deceleration of the vehicle, taking advantage of the startability by the electric motor in the hybrid vehicles.
However, even if an automatic stop condition is satisfied, such stop/start-up controlling devices fail to stop the engine in some cases, according to the value set for the automatic stop condition. This brings about yet further inconveniences from unstable functioning.
To obviate or minimize the above inconvenience, the present invention provides an automatic stop/start-up controlling device for an engine, having a transmission arranged with an engine mounted on a vehicle through a clutch, the controlling device controlling to automatically stop the engine when an automatic stop condition is satisfied while the engine is driven, and controlling to automatically start up the engine when an automatic start-up condition is satisfied while the engine is automatically stopped. The automatic stop condition is satisfied when all of the following conditions are satisfied, the conditions being (1) vehicle speed is less than a set value other than zero, (2) an idle switch is on, and (3) a gear position of the transmission is in neutral. The automatic start-up condition is satisfied when any of the following conditions is satisfied, the conditions being (1) the clutch is changed to a disengaged state from a fully or half engaged state, (2) the gear position of the transmission is in non-neutral, (3) the idle switch is off, or (4) a condition of booster negative pressure.
The controlling device of the present invention is provided with the automatic stop and start-up conditions of the engine set appropriately, so that the automatic stop condition precisely stops the engine and the automatic start-up condition precisely starts up the engine without delay. This arrangement enables automatic stop/start-up control reflecting the operator""s driving intentions without the vehicle feeling incongruous due to start-up or shut-down of the engine. The arrangement also improves exhaust gas purification and fuel consumption performance.